This is why it's important to always make sure your visitors clear their void before they come over. This can be done by visiting any town that has ten villagers living in it. Always make sure to clear yours as well before visiting others
Yea, I accidentally picked up a villager I loathed because they were in boxes. Now I have to find a way to get rid of her ;-; It feels like visiting towns is a lot like making sure they don't have any sort of disease or illness.
I have two towns that I decided would only have 9 villagers. That was a mistake because I can never trade with people when I play them. I would be so annoyed if a 10th popped up. Both towns are completely decorated, so a new plot would definately end up in a horrible spot.